1. Field of the Invention
This invention relates generally to dishwashing machines and specifically to a novel rack support wheel assembly in a dishwashing machine.
2. Description of the Related Art
Machines used for washing articles, such as dishes, typically include one or more racks to support the articles. The racks comprise a lattice of bent metal rods or molded plastic formed to support the articles while permitting water from jet sprays to contact the articles. To facilitate loading and unloading of articles, the racks are adapted to be at least partially removed from the machine.
In a household dishwasher, for example, the dishes are washed in an enclosure or tub having a front door which pivots downwardly. A lower rack has wheels journalled thereon. The wheels rest on flanges in the tub and permit the lower rack to be rolled out of the tub onto the open door. An upper rack is provided with a track or flange supported by pairs of vertically spaced wheels or rollers mounted on the interior walls of the tub. The upper rack has wheels journalled thereon and resting on or inside the track or flange. Since the rack is movable relative to the track which moves relative to the tub, the telescoping action allows the upper rack to be rolled completely out of the tub while providing complete support on the wheels and tracks which form a cantilever arrangement.
The wheels journalled on the wall of the tub or enclosure are mounted with a screw inserted through a central hole in each wheel. Usually, a washer is placed over the screw. Because the washer and wheel are likely to fall off the screw during assembly, a portion of the screw is deformed to hold the washer in place. Thus, the wheel is secured between the washer and the head of the screw. The screw is then threaded or otherwise secured in the wall of the enclosure.
It has been found that deforming the screw during assembly is time consuming and requires costly tooling. Interruption of the assembly process for the deforming step and for tooling changes is also costly. An assembly of a wheel, axle, and washer can be difficult to manipulate into position for deforming the shaft. Thus, when deforming the shaft, it is possible to inadvertently deform the threads on the shaft thereby adversely affecting installation in the wall. Further, an edge of the shaft which seats against the wall may be inadvertently deformed so that it does not seat well.
Another means of mounting a roller in a washing machine tub is shown in U.S. Pat. No. 3,804,483 to Afful et al. A mounting stud has an outer bearing surface on which the roller rotates and an inner bore for receiving a threaded fastener. The roller is placed on the stud and resilient fingers on an edge of the stud are displaced to hold the roller on the stud. The stud is placed against a wall of the tub and the threaded fastener is secured in the bore through the wall. The stud is a complex component having relatively fragile fingers. In addition, the roller assembly is not complete until it is installed in the tub. That is, there are two pieces which are assembled with the tub wall, one from the inside and one from the outside.